1. Field of the Invention
The present invention relates to probing and analysis of semiconductor integrated circuits and in particular, to a method of extracting dopant profiles from cellular semiconductor structures.
2. Discussion of the Prior Art
Extraction of doping profiles from specified areas of semiconductor devices is a rather difficult task when the devices are only available in the form of individually diced semiconductor chips. Typically, such a task is encountered in the analysis of a given competitor sample, for example, for purposes of determining patent infringement, or in obtaining reference data for new process development.
Of the profiling techniques applicable to undiced semiconductor wafers, the most commonly used is the Spreading Resistance Probe (SRP) method. See R. G. Mazur and D. H. Dickey, "A Spreading Resistance Technique for Resistivity Measurements in Si", J. Electrochem. Soc., 113, 255 (1966). The Mazur/Dickey SRP method requires the wafer to have specially devised rectangular patterns of 1,000 .mu.m.times.100 .mu.m (preferred dimensions), or at least 200 .mu.m.times.40 .mu.m. See "How Big a Pattern Do We Need for Spread Resistance Analysis", Solecon Labs Technical Note, Jun. 7, 1990.
Unfortunately, the conventional SRP method cannot be applied to diced semiconductor structures, except for non-cellular, large-area power devices such as high-current diodes and thyristors.